Rapid Diagnostic tests are also called immunochromatographic strip (ICS) tests. They have been a popular platform for rapid tests since their introduction in the late 1980s. ICS tests are used for the specific qualitative or semi-quantitative detection of many analytes including antigens, antibodies, and even the products of nucleic acid amplification tests. One or several analytes can be tested for simultaneously on the same strip. Urine, saliva, serum, plasma, or whole blood can be used as specimens. Extracts of patient exudates or fluids have also been successfully used.
Test sensitivity can be quite good. For example, hepatitis B surface antigen (HBsAg) ICS tests have claimed a sensitivity of 1.0 ng HBsAg/ml or less. Test specificity can also be very high. The tests use colloidal gold, dye, or latex bead conjugates to generate signal. The assembled strips are dried and packaged, making them stable for months when properly protected from moisture and excessive heat.
To perform the test, a sample-either used alone or with an extraction reagent or running buffer-is placed on the sample pad on one end of the strip. The signal reagent is solubilized and binds to the antigen or antibody in the sample and moves through the membrane by capillary action. If specific analyte is present, the signal reagent binds to it, and a second antibody or antigen-immobilized as a line in the nitrocellulose-then captures the complex. If the test is positive, a pink/purple line develops.
Once the specimen is added, the tests can be left unattended until they are read. The tests can be run individually or in limited-size batches.
Results can usually be read in 5 to 15 minutes. All tests include an internal procedural control line that is used to validate the test result. Appearance of two lines, therefore, indicates a positive result, while a negative test produces only one line.
If the serum has a darker or redish color ,it is not pure serum any more. Please don’t use it, it will cause the wrong result. Answer: If the serum has a darker or redish color ,it is not pure serum any more. Please don’t use it, it will cause the wrong result.